Thin-film photovoltaic device with wavy monolithic interconnects

ABSTRACT

A thin-film optoelectronic module device ( 100 ) and design method comprising at least three monolithically-interconnected cells ( 104, 106, 108 ) where at least one monolithically-interconnecting line ( 250 ) depicts a spatial periodic or quasi-periodic wave and wherein the optoelectronic surface of said thin-film optoelectronic module device ( 100 ) presents at least one set of at least three zones ( 210, 220, 230 ) having curves of substantially parallel monolithic interconnect lines. Border zones ( 210, 230 ) have a lower front-contact sheet resistivity than th at of internal zone ( 220 ). Said curves of substantially parallel interconnecting lines may comprise peaks of triangular or rounded shape, additional spatial periods that are smaller than a baseline period, and mappings from one curve to the adjacent curve such as in the case of non-rectangular module devices ( 100 ). The device ( 100 ) and design method are advantageous to reduce costs and materials to manufacture thin-film optoelectronic module devices ( 100 ) while increasing production yield, reliability, aesthetic appearance, and range of applications.

FIELD OF THE INVENTION

The present invention relates to photovoltaic devices manufactured bydeposition of thin-films and more particularly to the design ofmonolithic interconnects between cells within a photovoltaic module.

BACKGROUND OF THE INVENTION

Photovoltaic devices are generally understood as photovoltaic cells orphotovoltaic modules. Photovoltaic modules ordinarily comprise arrays ofinterconnected photovoltaic cells.

Thin-film photovoltaic modules, a variety of which is also known asthin-film solar modules, are generally composed of a number ofelectrically interconnected optoelectronic components. Such componentsmay be optoelectronic devices such as photovoltaic cells and additionaloptional components such as diodes and other electronic devices.

Multilayer thin-film technologies enable the monolithic integration andinterconnection of several optoelectronic components and associatedcomponents on a same substrate. This integration is produced in situusing a sequence of layer deposition and scribing techniques. Thin-filmoptoelectronic or photovoltaic components or devices are essentiallycomposed of a stack of three material layers: a conducting back-contactelectrode layer, a semiconductive photovoltaic material layer, alsoknown as the absorber, and another conducting front-contact electrodelayer, said front-contact layer usually being transparent. Photovoltaiccells based on semiconductive material such as Cu(In,Ga)Se₂ (CIGS) orCdTe show promise for less expensive solar electricity, lower energypayback time, and improved life-cycle impact as compared to traditionalwafer-based silicon photovoltaic devices or solar cells.

Compared to wafer-based photovoltaic devices, monolithic photovoltaicmodules may have lower costs thanks to reduced material quantities usedby thin films, reduced labor costs of monolithic integration, and easeof automatic production of large quantities of photovoltaic modules, forexample using roll-to-roll manufacturing techniques. Further savings canbe obtained by increasing the relative area of photovoltaic componentsexposed to light, for example by reducing the area occupied byfront-contact grids that collect current over the photovoltaic cell'sfront-contact electrode, electrical interconnects between optoelectroniccomponents, and busbars. Photovoltaic module production yields may alsobe increased thanks to a reduction in the number of production steps,for example by reducing or eliminating the step where front-contactgrids are added.

Monolithic integration of series- or parallel-interconnected thin-filmphotovoltaic cells is a technology applied broadly in thin filmphotovoltaic module technology. U.S. patent application 2008/0314439describes a process to form series-interconnected cells on an insulatingsubstrate and using scribing operations, insulating ink, and conductiveink. Scribing is commonly done using mechanical or laser systems. U.S.patent application 2010/0065099 describes a different method toestablish series interconnects that also uses scribing operations andthe addition of resistive and conductive materials. U.S. patentapplication 2012/0234375 describes a glass-based, amorphous siliconthin-film solar module with a plurality of meandering grooves toestablish electrical interconnects between cells. US 2012/0234375presents a method and embodiments where meandering grooves may overlapwhen translated along one side of the substrate, i.e. the waves arespatially phase-aligned. Some embodiments in US 2012/0234375 present asmaller degree of bending of the waves from the center of the solarmodule toward the peripheral edges.

SUMMARY OF THE INVENTION

Monolithic interconnects are customarily composed in the prior art ofmostly parallel scribing lines. The present invention describes a classof monolithic interconnects made of wavy scribing lines. The waviness ofsaid monolithic interconnects in some regions of the photovoltaic modulemay be tuned to the zonal sheet resistivity of the front-contact layer.Such wavy monolithic interconnects may be advantageous for certainapplications and module sizes and reduce the need for front-contact gridfingers. The invention is also especially advantageous for thin-filmCIGS photovoltaic modules and presents embodiments where photovoltaicmodules are not rectangular.

This invention presents solutions to the problem of manufacturing highefficiency thin-film photovoltaic devices, especially flexiblephotovoltaic devices, and more precisely lower-cost, more reliable, andmore customizable photovoltaic modules. It is especially advantageousfor roll-to-roll manufacturing of photovoltaic modules.

An object of the invention is to provide methods to design andmanufacture a class of photovoltaic devices featuring wavy monolithicinterconnects. The distance between monolithic interconnect linesbetween photovoltaic cells of photovoltaic modules is a function of manyparameters such as electrical current, front-contact sheet resistivity,the presence of front-contact grid elements to increase conductivity,and monolithic interconnect resistivity. The invention thereforepresents solutions based on wavy monolithic interconnects to designphotovoltaic modules featuring few or no front-contact grids whileproviding photovoltaic module designers with a new method to designlower-cost photovoltaic modules of various sizes and shapes.

A first problem in the field of thin-film photovoltaic devices is thatthe transparent front-contact layer has a relatively high resistivity.Collection of electrons generated by the photovoltaic device is usuallyimproved by adding a conductive grid onto the front-contact. Gridfingers are designed to collect electrons generated within theirvicinity. The size and shape of this vicinity depends on severalparameters, the most important of which are transparent front-contactresistivity and grid shape. Design of efficient photovoltaic cells andmodules therefore requires the design of grids that are optimized to theshape and function of the photovoltaic modules and the interconnectedcells that compose it.

A second problem in the field of thin-film photovoltaic devices is thatdepositing a grid onto the front-contact requires a manufacturing stepsuch as screen printing. This step represents additional costs, requiresspecific machines, and as such may reduce production yield.

A third problem in the field of thin-film photovoltaic devices is thatthe grid, because it is opaque and deposited onto the transparentfront-contact, must be made as narrow as possible so as to minimizemasking of the underlying semiconductor absorber layer wherephotovoltaic conversion occurs. The grid, although it increases overallcollection of charges, reduces the amount of photovoltaic conversionwithin the absorber layer.

A fourth problem in the field of thin-film photovoltaic devices is thatthe grid may not bind perfectly with the front-contact layer andimperfections in the interface may present locations with substandardconductivities, thereby reducing the local benefit of a given gridsegment or finger.

A fifth problem in the field of flexible thin-film photovoltaic devicesis that they are encapsulated between adhesive flexible sheets. Thefront transparent sheet therefore adheres to the grid. As the module isflexed or subject to strain, for example through differential thermalexpansion, the front transparent sheet may cause strain on the grid,rupture the contact between grid and front-contact, and therefore reducethe overall module's photovoltaic efficiency and reliability.

A sixth problem in the field of thin-film photovoltaic devices is thatphotovoltaic modules having a large distance between anode and cathodeand comprising monolithic serially-interconnected cells may have a highvoltage due to the large number of narrow cells interconnected betweenthe module's anode and cathode.

A seventh problem in the field of photovoltaic devices is that a uniformcolor appearance of photovoltaic cells or modules might be desired, forexample for aesthetic purposes, and it might be desirable to minimizethe number of grid lines which may introduce visible non-uniformities.

Finally, an eighth problem in the field of photovoltaic devices is thatrectangular or square photovoltaic devices may not always completelycover surfaces containing curves, thereby resulting in overallefficiency loss for a given area. It may therefore be desirable toobtain non-rectangular modules, such as modules designed with featuresmatching the shape of the surface to be covered, so as to maximize thearea producing photovoltaic electricity and therefore increasing theoverall fill factor.

The invention thus pertains to monolithically-interconnected thin-filmphotovoltaic devices that, thanks to specific sizing and shaping of thephotovoltaic cells and of monolithic interconnects between cells, alongwith tuning of front-contact layer sheet resistivity, can bemanufactured with less or no front-contact grids.

In greater detail, the invention provides a thin-film optoelectronicmodule device comprising at least three optoelectronic components orcells, such as photovoltaic, diode, or light-emitting diode components,that are monolithically interconnected in series and such that whenviewed along a viewing axis substantially orthogonal to theoptoelectronic surface of said thin-film optoelectronic module device,at least one monolithic interconnect line, delimited by an isolatingback-contact groove in the electrically conductive back-contact layerand an isolating front-contact groove in the electrically conductivefront-contact layer, represents a curve depicting a spatial periodic orquasi-periodic wave of at least one spatial half-period, the largestpeak-to-peak amplitude of which is at least eight times that of theshortest distance between said back-contact groove and saidfront-contact groove of said monolithic interconnect line and wherein,between a first busbar and a second busbar of the optoelectronic moduledevice, the optoelectronic surface of said thin-film optoelectronicmodule device presents at least one set of at least three zones ofsubstantially parallel monolithic interconnect lines that each depict aperiodic or quasi-periodic wave of at least one spatial half-periodhaving a largest amplitude wave component or (e.g. in the case where awave of lower amplitude and higher frequency is superimposed on adominant wave) a baseline largest amplitude wave component of spatialperiod λ, said set being visually segregated into: (a) an internal zonecomprising at least one monolithic interconnect line which optionallydelimits the internal zone and, (b) border zones, between the internalzone and each busbar, each border zone comprising at least onemonolithic interconnect line that is substantially parallel tomonolithic interconnect lines of said internal zone and where theamplitude of said largest amplitude wave component of at least one saidmonolithic interconnect line within said border zones is decreased withrespect to that of the adjacent monolithic interconnect line that iscloser to or comprised in said internal zone, and decreases for eachsaid line that is located closer to the optoelectronic module device'sbusbar, wherein within the border zones there is a lower front-contactsheet resistivity than in the internal zone.

The device may comprise an electrically insulating layer positionedeither as a substrate under, or as a superstrate on top of, thefollowing stack of layers (a), (b), (c): namely (a) a front-contactlayer comprising at least one first and at least one second electricallyconductive front-contact components, said first and second front-contactcomponents being separated by at least one front-contact groove makingat least one first front-contact component and at least one secondfront-contact component that are electrically separate; (b) an absorberlayer comprising at least one semiconductive optoelectronically activelayer; (c) a back-contact layer comprising at least one firstelectrically conductive back-contact component and at least one secondelectrically conductive back-contact component deposited onto saidelectrically insulating layer wherein said first back-contact componentand second back-contact component are separated by at least oneback-contact groove making said first back-contact component and secondback-contact component electrically separate, thereby realizing a firstoptoelectronic component and a separate second optoelectronic componenteach comprising a stack of said front-contact component, at least onesaid semiconductive layer, and said back-contact component; and suchthat at least one monolithic interconnection connects at least one ofsaid first front-contact components, passing through said semiconductivelayer, with at least one said second back-contact components, therebyrealizing a series-interconnection between a first optoelectroniccomponent and a second optoelectronic component.

The device may also comprise at least one said back-contact groove or atleast one said front-contact groove that, when viewed along a viewingaxis substantially orthogonal to the optoelectronic surface of saidthin-film optoelectronic module device represented by at least onemonolithic interconnect line, depicts a curve comprising at least onepeak of triangular shape.

The device may also comprise at least one said back-contact groove or atleast one said front-contact groove that, when viewed along a viewingaxis substantially orthogonal to the optoelectronic surface of saidthin-film optoelectronic module device, represented by at least onemonolithic interconnect line, depicts a curve comprising at least onepeak of rounded shape, said peak having a radius of curvature that isless than the peak's width at tenth of maximum amplitude.

The device may further comprise at least one said monolithicinterconnect line that comprises at least one additional wave of spatialperiod smaller than half of that of said largest amplitude wavecomponent.

At least one said monolithic interconnect of the device may be drawn tosubstantially correspond to a mathematical mapping of at least one othersaid monolithic interconnect line.

Also, at least one said monolithic interconnect line of the device maybe drawn to substantially correspond to a mathematical radialtransformation of at least one other said monolithic interconnect line.

The device may further comprise at least one metalized grid componentmade of at least one metalized trace deposited onto at least one saidfront-contact component.

More specifically with respect to said monolithic interconnect lines, aline segment comprised within said monolithic interconnect line may be acontinuous groove filled with conductive material and substantiallyparallel to a monolithic interconnect line.

More specifically with respect to said absorber layer, at least onesemiconductive photovoltaic layer of the device may be made ofCu(In,Ga)Se₂ semiconductor ordinarily referred to as CIGS.

In further detail with respect to said monolithic interconnect lines, aline segment comprised within said monolithic interconnect line may be asegmented line of holes substantially representing a dash pattern thatis substantially parallel to the monolithic interconnect line andwherein at least one of said holes comprises a wall made of acopper-rich amorphous metallic compound of solidified CIGS melt stemmingfrom said semiconductive optoelectronically active layer made of CIGSmaterial.

The invention also concerns a method for the design of thin-filmoptoelectronic module devices comprising at least threeseries-interconnected optoelectronic components or cells, such asphotovoltaic, diode, or light-emitting diode components, the methodcomprising monolithically interconnecting said components in series suchthat when viewed along a viewing axis substantially orthogonal to theoptoelectronic surface of said thin-film optoelectronic module device,at least one monolithic interconnect line, delimited by an isolatingback-contact groove in the electrically conductive back-contact layerand an isolating front-contact groove in the electrically conductivefront-contact layer, represents a curve depicting a spatial periodic orquasi-periodic wave of at least one spatial half-period, the largestpeak-to-peak amplitude of which is at least eight times that of theshortest distance between said back-contact groove and saidfront-contact groove of said monolithic interconnect line and wherein,between a first busbar and a second busbar of the optoelectronic moduledevice, the optoelectronic surface of said thin-film optoelectronicmodule device presents at least one set of at least three zones ofsubstantially parallel monolithic interconnect lines that depict aperiodic or quasi-periodic wave of at least one spatial half-periodhaving a largest amplitude wave component or a baseline largestamplitude wave component of spatial period λ, said set being visuallysegregated into: (a) an internal zone comprising or delimited by atleast one monolithic interconnect line and, (b) border zones, betweenthe internal zone and each busbar, said border zones each comprising atleast one monolithic interconnect line that is substantially parallel tomonolithic interconnect lines of said internal zone and where theamplitude of said largest amplitude wave component of at least one saidmonolithic interconnect line within said border zones is decreased withrespect to that of the adjacent monolithic interconnect line that iscloser to or comprised in said internal zone, and decreases for eachsaid line that is located closer to the optoelectronic module device'sbusbar providing border zones wherein there is a lower front-contactsheet resistivity than in the internal zone; said method furthercomprising the iterative computation of the number of said cells of saidthin-film optoelectronic module device, the width of said cells, and,within at least one border zone over a peak-to-peak half spatial periodλ/2 of said quasi-periodic wave of at least one pair of substantiallyparallel monolithic interconnect lines, the distance between cells atthe divergent and convergent sides of at least one of said wave'speak-to-peak half spatial period.

The method can also comprise for said optoelectronic module devicepositioning an electrically insulating layer either as a substrateunder, or as a superstrate on top of, the following stack of layers (a),(b), (c): namely (a) a front-contact layer comprising at least one firstand at least one second electrically conductive front-contactcomponents, said first and second front-contact components beingseparated by at least one front-contact groove making at least one firstfront-contact component and at least one second front-contact componentthat are electrically separate; (b) an absorber layer comprising atleast one semiconductive optoelectronically active layer; (c) aback-contact layer comprising at least one first electrically conductiveback-contact component and at least one second electrically conductiveback-contact component deposited onto said electrically insulating layerwherein said first back-contact component and second back-contactcomponent are separated by at least one back-contact groove making saidfirst back-contact component and second back-contact componentelectrically separate, thereby realizing a first optoelectroniccomponent and a separate second optoelectronic component each comprisinga stack of said front-contact component, at least one saidsemiconductive layer, and said back-contact component; and such that atleast one monolithic interconnection connects at least one of said firstfront-contact components, passing through said semiconductive layer,with at least one said second back-contact components, thereby realizinga series-interconnection between a first optoelectronic component and asecond optoelectronic component.

The method can further comprise computation of at least one dimensionthat represents a characteristic size of the optoelectronic cells thatcan be carried out using input values for front-contact sheetresistivity, back-contact sheet resistivity, initial cell width, andmonolithic interconnect line width.

Said computation can also be carried out using at least one repeatablecomputation of the photovoltaic characteristics of a cell segment model,said cell segment model comprising at least one finite element cellsegment.

Furthermore said computation can comprise at least one repeatablecomputation where photovoltaic conversion efficiency of the thin-filmoptoelectronic module device is maximized.

The invention's features advantageously solve several problems in thefield of monolithically-interconnected thin-film photovoltaic devices,namely:

-   -   Said invention reduces or cancels the need for front-contact        grids and therefore reduces or cancels the effort needed to        design said grids, hence reducing design costs.    -   Said invention reduces or cancels the manufacturing step needed        to deposit a grid onto the front-contact, hence reducing        manufacturing complexity and costs.    -   Said invention reduces or cancels the need for front-contact        grids and therefore increases the light-exposed area of the        semiconducting photovoltaic layer resulting, for a certain class        of photovoltaic modules, in increased module efficiency.    -   Said invention may increase the manufacturing yield by reducing        the number of elements, namely the grid, needed for a        photovoltaic module.    -   Said invention may increase the overall reliability of flexible        thin-film photovoltaic devices by reducing or canceling a number        of points of failure introduced by the addition of front-contact        grids.    -   Said invention may reduce the number of serially-interconnected        cells within a thin-film photovoltaic module and therefore help        reduce high voltage problems resulting from the high number of        cells in modules that have a large distance between anode and        cathode.

BRIEF DESCRIPTION OF FIGURES

Embodiments of the invention will now be described by way of example,with reference to the accompanying drawings, in which:

FIG. 1A shows a cross-section of a photovoltaic cell.

FIGS. 1B-1E show cross-sections of monolithically-interconnectedphotovoltaic modules.

FIGS. 2A-2H show top views of photovoltaic modules comprisingmonolithically-interconnected cells.

FIGS. 2I-2J represent top views of part of or entire photovoltaicmodules used for the description of the design method.

FIGS. 3A-3C represent magnified top views of interconnections withinmonolithically-interconnected photovoltaic modules.

FIGS. 4A-4C represent magnified top view sections of a module'smonolithically interconnecting lines to explain the computationalprocess used to design embodiments of the invention.

FIGS. 5A-5B are flowcharts describing a method that can be used to modeland design an embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 1A shows an embodiment of a thin-film photovoltaic cell 100. FIG.1A is represented for explanatory purposes to clarify the layerstructure of a typical photovoltaic cell. A sequence of material layersis deposited on a substrate 110. Substrate 110 may be rigid or flexibleand be of a variety of materials or coated materials such as glass,coated metal, plastic-coated metal, plastic, or coated plastic such asmetal-coated plastic. The inventive method as described is especiallyadvantageous for flexible materials such as plastic, metal, or flexibleglass. A preferred flexible substrate material is polyimide as it isvery flexible, sustains temperatures required to manufacture highefficiency optoelectronic modules, requires less processing than metalsubstrates, and exhibits thermal expansion coefficients that arecompatible with those of material layers deposited upon it. Industriallyavailable polyimide substrates are ordinarily available in thicknessesranging from 7 μm to 150 μm. An exemplary sequence of material layerdeposition follows. The order of this sequence may be reversed andordinarily includes scribing operations to delineate cell or modulecomponents. The purpose of this initial description is to clarify thecontext within which the monolithic interconnect design, the mainsubject of this invention, is executed.

Substrate 110 is ordinarily coated with at least one electricallyconductive layer 120. Said electrically conductive layer, or stack ofelectrically conductive layers, also known as the back-contact, may beof a variety of electrically conductive materials, preferably having acoefficient of thermal expansion (CTE) that is close both to that of thesaid substrate 110 onto which it is deposited and to that of othermaterials that are to be subsequently deposited upon it. Conductivelayer 120 preferably has a high optical reflectance. In ordinarypractice, layer 120 is deposited in a process such as sputtering,electrodeposition, chemical vapor deposition, physical vapor deposition,electron beam evaporation, or spraying and is commonly made of Moalthough several other thin-film materials such as metal chalcogenides,molybdenum chalcogenides, molybdenum selenides (such as MoSe₂),transition metal chalcogenides, tin-doped indium oxide (ITO), doped ornon-doped indium oxides (such as In₂O₃), doped or non-doped zinc oxides,zirconium nitrides, tin oxides, titanium nitrides, Ti, W, Ta, and Nb mayalso be used or included advantageously.

In the next step at least one semiconductive photovoltaic layer 130,also known as the absorber layer, is deposited onto said back-contact.Layer 130 may for example be made of an ABC material, wherein Arepresents elements in group 11 of the periodic table of chemicalelements as defined by the International Union of Pure and AppliedChemistry including Cu or Ag, B represents elements in group 13 of theperiodic table including In, Ga, or Al, and C represents elements ingroup 16 of the periodic table including S, Se, or Te. An example of anABC₂ material is the Cu(In,Ga)Se₂ semiconductor also known as CIGS.Other thin-film absorber materials include CdTe and its variants,amorphous silicon, thin-film silicon, as well as absorber materials usedto manufacture dye-sensitized solar cells or organic solar cells. Layer130 may be deposited using a variety of techniques such as sputtering,electrodeposition, printing, or as a preferred technique for an ABCmaterial, vapor deposition.

The subsequent steps ordinarily include the deposition of substantiallytransparent layers. In the case of an ABC or a CdTe absorber material, afirst layer stack ordinarily includes at least one so-calledsemiconductive buffer layer 140, ordinarily with an energy bandgaphigher than 1.7 eV, for example made of CdS, indium sulfides, zincsulfides, gallium selenides, indium selenides, tin oxides, zinc oxides,or Zn(O,S) material. For most absorbers the front-contact layer stackordinarily includes a transparent conductive oxide (TCO) layer 150, forexample made of materials such as doped indium oxide, doped galliumoxide, or doped zinc oxide. Further optional steps include thedeposition of front-contact metallized grid traces 160 to advantageouslyaugment front-contact conductivity followed by anti-reflective coatingordinarily provided either as a deposited layer or as an encapsulatingfilm.

FIGS. 1B to 4C depict cross-sections and top views of exemplaryembodiments of the invention. Someone skilled in the art will appreciatethat the scales of the various components represented in the figureshave been changed to improve clarity. Furthermore, the number and areasof components in the figures are highly variable and would be scaled upin the framework of an industrial production.

FIG. 1B shows a cross-sectional cut-out of an embodiment of an extendedmonolithically interconnected photovoltaic module 100 that comprisesthree series-interconnected optoelectronic devices 104, 106, 108. Saidoptoelectronic devices 104, 106, 108 may be photovoltaic devices,diodes, or light-emitting diodes. An embodiment of said photovoltaicmodule 100 would contain at least two of said optoelectronic devices,preferably several of said optoelectronic devices. In a preferredembodiment said optoelectronic devices are photovoltaic devices, alsoknown as solar cells. The process to manufacture photovoltaic device 100comprises a sequence of layer deposition steps and scribing steps 121,131, 151. Electrically insulating substrate 110 is initially coated withelectrically conductive back-contact layer 120. Grooves 121 are then cutinto back-contact layer 120 so as to expose at least one continuous lineof substrate 110, thereby providing a set of back-contact components124, 126, 128. The process step where grooves 121 are cut is referred toas scribing or patterning step P1. Patterning step P1 may be done usinga mechanical scribing blade, preferably using a laser, more preferablyusing a pulsed laser such as a nanosecond or picosecond laser. In thenext step, absorber layer 130 is deposited onto said back-contactcomponents, thereby also filling grooves 121. Deposition of absorberlayer 130 may, for some absorber materials such as CIGS or CdTe, befollowed by the deposition of buffer layer 140. Grooves or holes 131 arethen cut or drilled into layers 130 and, if present, simultaneouslythrough layers 140. The process step where grooves or holes 131 are cutis referred to as scribing or patterning step P2. Patterning step P2 maybe done using the same tools as for step P1 but possibly with someadjustments that a person skilled in the art will know how to determine.In case a continuous groove is made, care must be taken not to damagethe underlying back-contact components 124, 126, 128. In the next stepfront-contact layer stack 150 is deposited onto said buffer layer 140 ifit is present or said absorber layer 130, thereby filling grooves orholes 131 and establishing an electrically conducting connection betweensaid front-contact layer stack 150 and said back-contact components 124,126, 128. In scribing step P3, front-contact grooves 151 are thenscribed into front-contact layer stack 150 and extend deep enough toexpose continuous lines of at least one of said semiconductive layers130, 140, thereby separating said front-contact layers into electricallydisconnected front-contact components 152, 154, 156, 158 and possibly,because buffer layer 140 is ordinarily only a few nanometers thick, intobuffer layer components 142, 144, 146, 148. Scribes 121, 131, 151 areordinarily done as close as possible to each other so as to minimize thearea that will subsequently not be available for photovoltaicconversion. The result of the manufacturing process illustrated in FIG.1B is a photovoltaic module 100 comprising series-interconnectedphotovoltaic cells 104, 106, 108.

In summary, a monolithic interconnect comprises a front-contactcomponent 154, 156 that is electrically connected via a line 131 ofempty or filled holes or grooves 132 to a back-contact component 126,128 and where each said front- and back-contact components areelectrically separated by scribed grooves 151, 121 from respectivelyadjacent front- and back-contact components.

FIG. 1C represents a variation of the embodiment presented in FIG. 1Bresulting from a variation of the method described for FIG. 1B. FIG. 1Cdiffers from FIG. 1B in that scribing step P2, resulting in grooves orholes 132, is done after deposition of front-contact layers 150. FIG. 3Bor 3C present a top view of a detail of FIG. 1C. Of interest is that theedges 133 of grooves or preferably holes 132 become conductive as aresult of heat transfer during the laser scribing process, therebyestablishing an electrical path between said front-contact layer stack150 and said back-contact components 124, 126, 128. For example, in thecase of a CIGS-type semiconductive photovoltaic layer, the conductivesurface of said grooves or holes 132 is a copper-rich amorphous metalliccompound of solidified CIGS melt stemming from the CIGS absorber layer130. Scribing step P3 of grooves 151 may be conducted before, at thesame time, or after scribing step P2. As in FIG. 1B, scribes 121, 131,151 are done close to each other and the result is a photovoltaic module100 comprising series-interconnected photovoltaic cells 104, 106, 108.FIG. 1D represents a variation of the embodiment presented in FIG. 1Cresulting from a variation of the method described for FIG. 1C. FIG. 3Bor 3C also present a top view of a detail of FIG. 1D. FIG. 1D differsfrom FIG. 1C in that scribing step P2 results in holes 132 that maypuncture back-contact layer 120 and therefore back-contact components124, 126, 136. A benefit of this method is that it may use higher energyscribing lasers and be executed faster than that presented in FIG. 1C.Only holes and not grooves along the module's full width are appropriatefor this method. Front-contact to back-contact electrical interconnectis provided by conductive hole edges 133, the properties of which aresimilar to those of FIG. 1C.

FIG. 1E represents a variation of the embodiment presented in FIG. 1Cresulting from a variation of the method described for FIG. 1C. FIG. 1Ediffers from FIG. 1C in that a conductive paste 163 fills holes orgrooves 132 to supplement the electrical conductivity of front-contactto back-contact interconnects provided by conductive hole edges 133. Themethod presented in FIG. 1E may also be applied to that presented inFIG. 1D so as to also supplement conductivity of conductive hole edges133.

FIGS. 2A to 2J present the main inventive contribution of the invention:top views of photovoltaic modules comprising narrow photovoltaic cellsinterconnected by wave-shaped monolithic series-interconnects such asthose presented in FIGS. 1B, 1C, 1D, 1E. The shape of the waves tracedby the monolithic interconnects may be triangular or smoother such assine waves or smoothed triangles. Zones 210, 230 may have lowerfront-contact sheet resistivity than zone 220.

FIG. 2A presents the top view of a photovoltaic module 100 comprising anumber of monolithic interconnect lines 250 corresponding in this figureto a triangle waveform. Each monolithic interconnect line 250 should beunderstood as representing a series monolithic interconnect betweenadjacent cells such as optoelectronic devices 104, 106, 108 presented inFIGS. 1B, 1C, 1D, 1E. Monolithic interconnect lines 250 can be seen aswaveforms that comprise a number of peaks of triangular shape 251.Module 100 comprises 3 zones 210, 220, 230 of monolithic interconnectlines between photovoltaic module busbars 215, 235, ordinarily locatedat the module's outer edge. In photovoltaic module 100, electricalcurrent therefore flows, for example, from busbar 215 at the end of zone210 to busbar 235 at end of zone 230. Zone 220 can be understood as aninternal zone of module 100 characterized in that the waves drawn by themonolithic interconnect design are of constant amplitude and spatialfrequency. Zones 210 and 230 are characterized in that the amplitude ofthe waves decreases progressively from the outer edge of the internalzone 220 of module 100 to the outer edge of said module. For example,monolithic interconnect lines of zones 210, 230 may derive fromconformal or nonconformal mappings of monolithic interconnect lines ofzone 220. Waveforms in zones 210, 220, 230 all have the same dominantspatial frequency. It is possible however to conceive waveformscontaining additional frequencies along all or part of a givenmonolithic interconnect line.

Because in zones 210, 230, the distance between monolithic interconnectlines 250 may be greater than optimal, thereby resulting in increasedresistance of the front-contact layer, one may decide upon deposition ofthe front-contact layer 150 to manufacture a layer of lower sheetresistivity in zones 210, 230. Lower sheet resistivity may for examplebe obtained by deposition of a thicker front-contact layer in zones 210,230. For example if in zone 220 the sheet resistivity is 30 ohms persquare, in zones 210, 230 the sheet resistivity may be comprised between15 and 20 ohms per square. This tuning of sheet resistivity may beespecially feasible and advantageous for roll-to-roll production ofsolar modules longer than one meter, depending on front-contactdeposition machine technologies.

FIG. 2B presents a variation of FIG. 2A where the dominant trianglewaveform of FIG. 2A is replaced by a sinusoidal waveform. Monolithicinterconnect lines 250 therefore comprise a number of peaks of roundedshape 252. This design, in which the trace of monolithic interconnectlines 250 is smoother than that presented in FIG. 2A, may beadvantageous for some manufacturing installations in that the waveformpresents no sharp edges and may be easier and faster to manufacture bythe scribing laser. A person skilled in the art will infer that othertypes of smooth curves may be used for said waveform. Similarly to FIG.2A, zones 210 and 230 are characterized in that the amplitude of thewaves decreases progressively from the outer edge of the central zone220 of module 100 to the outer edge of said module.

FIG. 2C presents a variation of FIG. 2A where the dominant trianglewaveform of FIG. 2A is modified in zones 210 and 230 by adding smalleramplitude waveforms 270, such as triangle waveforms, to the dominanttriangle waveform at desirable locations. For example a desirablelocation is where in FIG. 2A the local distance from one monolithicinterconnect line 250 to another is greater than a certain thresholdvalue. This may for example occur at or near the troughs or peaks ofwavy monolithic interconnect lines 250 within zones 210 and 230,respectively. Furthermore, conductivity may be increased in some regionswith the addition of optional grid lines 260.

FIG. 2D presents a variation of FIG. 2B where grid lines 260 have beenadded to some regions where the local distance from one monolithicinterconnect line 250 to another is greater than a certain thresholdvalue.

FIG. 2E presents a variation of FIG. 2A where the dominant trianglewaveform of FIG. 2A is modified by flattening peaks and troughs ofmonolithic interconnect lines 250 in zones 210 and 230, respectively.

FIG. 2F presents a variation of FIG. 2B where the sinusoidal waveformsof monolithic interconnect lines 250 comprise a dominant frequency andbaseline largest amplitude similar to that of monolithic interconnectlines 250 of FIG. 2B and at least one additional frequency of loweramplitude and higher frequency than that of the dominant frequency. Saidadditional frequency may have different values of amplitude andfrequency from one monolithic interconnect line 250 to another.Furthermore, similarly to what is presented in FIG. 2E, peaks andtroughs of the dominant and non-dominant frequency waves may beflattened or smoothed, for example to improve the blending of wavymonolithic interconnect lines 250 in the vicinity of anode or cathodeedges such as in zones 210 and 230 of photovoltaic module 100. Waves maybe smoothed at selected locations such as peaks of the dominant wavecomponent by redesigning interconnect lines to improve blending or, morepreferably, by using numerical smoothing methods or filters ordinarilyused to smooth signals or data sets. Said smoothing methods or filtersmay be, for example, local regression methods such as LOESS, low-passfiltering, kernel-based or matrix-based smoothing, Kalman filtering,spline smoothing, Butterworth or Chebyshev filtering, and variousdigital or numerical filtering methods.

FIG. 2G presents a variation of FIG. 2E where the shape of photovoltaicmodule 100 is not rectangular and includes at least one curved edge.FIG. 2G illustrates how the design of the dominant waveform ofmonolithic interconnects 250 can be adapted to a variety of topologies,such as that of an L-shaped photovoltaic module that may be part of anassembly of interconnected photovoltaic modules integrated onto asurface that comprises curved contours. Similarly to FIG. 2E,photovoltaic module 100 comprises three zones 210, 220, 230 ofmonolithic interconnect lines 250 between photovoltaic module busbars215, 235. Monolithic interconnect lines 250 are designed as trianglewaveforms aligned with radial axes converging approximately towards thecenter of revolution around which said L-shaped photovoltaic module isdesigned. Monolithic interconnect lines 250 may therefore be designed tosubstantially correspond to a mathematical radial transformation of atleast one other said monolithic interconnect line 250. To satisfy themaximum distance constraint between lines 250, the amplitude of theirwaveform increases with distance from said center of revolution aroundwhich the L-shaped photovoltaic module is designed. Furthermore, FIG. 2Gillustrates the addition of a smaller waveform 270 in regions where thedistance between lines 250 would be larger due to divergence of saidradial axes. For compatibility with FIG. 2E, FIG. 2G also illustratesthe use of optional grid lines 260 to increase front-contactconductivity of areas where the line-to-line distance is greater thanthe maximum distance constraint between lines 250.

FIG. 2H presents an intermediate variation of FIGS. 2A and 2G where theshape of photovoltaic module 100 is substantially trapezoidal andincludes at least one busbar 235 that is not parallel to the oppositebusbar 215. Similarly to FIG. 2A, photovoltaic module 100 comprisesthree zones 210, 220, 230 of monolithic interconnect lines 250 betweenphotovoltaic module busbars 215, 235. Similarly to FIG. 2G, FIG. 2Hillustrates the addition of a smaller waveform 270 in regions of thetrapezium's long side where the distance between lines 250 is larger. Atrapezoidal photovoltaic module may be advantageous to increase coverageof non-rectangular supporting structures.

FIG. 2I presents some of the cell and waveform parameters used to tracethe invention's monolithic interconnect lines. FIG. 2I represents twopartial and parallel monolithic interconnect lines 250 characterized bypeaks 251 of triangular shape as represented in FIGS. 2A, 2C, 2E, 2G.Triangular shapes have been chosen only for the figure's clarity and aperson skilled in the art will infer that the representation may alsoapply as an approximation to smooth or rounded waveforms as representedin FIGS. 2B, 2D, 2F with peaks of rounded shape 252. The waveform ischaracterized by a peak-to-peak height h 273 and a spatial period λ 573.The angle α 572 of the waveform's triangle may also be computed from tanα=λ/2h or, in the case of rounded waveforms, approximated. The distanceseparating each monolithic interconnect line 250 may be measured as Wc504 in a direction orthogonal to the waveform's supporting axis or tothe direction in which said spatial period λ is measured. Wc_seg 543 isa measure of the separation between two substantially parallel waveformsegments and is in practice measured orthogonally to the waveformsegment under consideration. Sc_sub 567 is a hatched out regionrepresenting the area where the separation between points on a firstmonolithic interconnect line 250 and a second monolithic interconnectline 250 is suboptimal for photovoltaic conversion and/or electricaltransfer.

FIG. 2J is a redraw of FIG. 2A where two regions 211, 231 arerepresented hatched out to designate the fact that photovoltaicconversion and/or electrical transfer is suboptimal in those regions.Regions 211, 231 ordinarily correspond to zones 210, 230, respectively.

FIGS. 3A, 3B, 3C present simulated magnified top views 300 of straightsegments of monolithic interconnect lines 250 comprised in photovoltaicmodule embodiments presented in FIGS. 1B to 1E and 2A, 2C, 2E, 2G and asspecifically indicated in FIG. 2I.

An equivalent magnified top view of monolithic interconnect lines 250comprised in photovoltaic module embodiments presented in FIGS. 2B, 2D,2F would present curved segments. Each monolithic interconnect linecomprises a set of three scribing traces 121, 131, 151 which correspondto traces 121, 131, 151 in FIGS. 1B to 1E. Because these are top views,front-contact components 152, 154 are also partly visible. Optionalfront-contact grids are not represented.

FIG. 3A shows two monolithic interconnect lines 250 each comprisingthree scribing traces 121, 131, 151 as continuous uninterrupted lines.This figure therefore corresponds to cross-sections presented in FIG.1B, 1C, or 1E.

FIG. 3B is similar to FIG. 3A with the difference that scribing traces131 are segmented into dot-shaped holes 132. This figure corresponds tocross-sections presented in FIGS. 1B to 1E.

FIG. 3C is similar to FIG. 3B with the difference that scribing traces131 are segmented into elongated dot- or dash-shaped holes 132. Thisembodiment with segments or elongated dots may be more advantageous thanthat presented in FIG. 3B in that traces 131 may be scribed faster.

FIG. 4A presents a cut-out from FIG. 2A and serves to indicateparameters useful to the design of the invention. The cut-out covers apeak-to-peak half spatial period λ/2 of the waveform of a monolithicinterconnect line 250. The length L_m 562 of photovoltaic module 100 isdefined as cumulated distance from a first busbar 215 to a second busbar235. In the case of a rectangular photovoltaic module L_m is simply thedistance between parallel busbars 215 and 235. In the case of anon-rectangular module cut-out where, for example, busbars 215, 235 arenot parallel, the distance L_m may be a cumulative measure of averagedistances Wc 504 between the supporting lines of the waveforms ofadjacent monolithic interconnect lines 250.

FIG. 4B presents an enlarged cut-out from FIG. 4A and serves to presentcomputation variables mentioned in FIG. 5B. Measure 575 represents thedistance Wc_sub_div_1 between adjacent monolithic interconnect lines 250at the divergent side of a waveform's half-period. In FIG. 4B thismeasure is shown between first busbar 215 and the first monolithicinterconnect line 250. Similarly, 576 represents the distanceWc_sub_con_1 between adjacent monolithic interconnect lines 250 at theconvergent side of a waveform's half-period.

FIG. 4C presents an enlarged cut-out from FIG. 4A and serves to presentan example of a finite element mesh 400 used for the computation of theelectrical properties of photovoltaic module 100. The mesh comprisesmonolithic interconnect nodes 450 located on monolithic interconnectlines 250, intra-nodes 410 located between adjacent monolithicinterconnect lines 250, and semiconducting finite element mesh segments420 joining nodes of mesh 400.

FIG. 5A is the first part of a flowchart describing a method that can beused to model and design an embodiment of the invention. The initialparameters comprise front-contact sheet resistivity 501, back-contactsheet resistivity 502, cell I-V data 503 which ordinarily is obtainedfrom the current vs. voltage curve of a real photovoltaic cell, aninitial cell width 504, and a monolithic interconnect line width 505which ordinarily is a measure of the width of a monolithic interconnectline 250.

A photovoltaic cell 104, 106, 108 is modeled as a set of cell segmentmodels 520. The modeling effort consists in adjusting model variables toapproximate cell I-V data 503. A cell segment model 520 may for exampleextend across a photovoltaic cell from a first monolithic interconnectline to a second monolithic interconnect line. A cell segment model 520may also be a chain of mesh segments 420 extending from a firstmonolithic interconnect line 250 to a second monolithic interconnectline 250, as represented in FIG. 4B. A cell segment model 520 istherefore discretized into a number of finite element cell segments 521which may be modeled by a person skilled in the art as a network ofone-diode models that comprise a current generator I_L, a diode D, ashunt resistor R_SH, a front-contact resistor R_FC, and a back-contactresistor R_BC. For example, a cell segment model may be composed of achain of one hundred finite element cell segments 521. A person skilledin the art will also know how to adjust said one-diode model torepresent monolithic interconnect nodes 450.

The maximum power point, photovoltaic efficiency, and photovoltaicefficiency over one year are then computed for cell segment models 520at steps 531, 532, and 533, respectively. The cell segment width is thenincremented at step 537 and computations 520, 531, 532, 533 repeateduntil reaching a maximum cell segment width 506 at which point theiterative computation branches out through decision 534. An alternativemay also be to decrement cell segment width at step 537 until reaching aminimum cell segment width 506 prior to branching out on minimum atdecision 534. This is followed by a selection of the cell segment widthwith maximum photovoltaic efficiency at step 535, thereby producing amaximum efficiency cell segment width Wc_seg 543, and followed furtherby a computation of I-V characteristics for the selected cell segmentwidth at step 536, thereby producing a cell segment's voltage value atmaximum power point Vmpp_seg 541 and a cell segment's current value atmaximum power point Impp_seg 542.

FIG. 5B is the second part of the flowchart in FIG. 5A. It uses resultVmpp_seg 541 from FIG. 5A and desired module voltage value at maximumpower point Vmpp_m 544 to compute, for example with a simple division,the initial number of cells in module Nc_m 561 at computational step550. Further parameters comprise the length of the module L_m 562,measured from busbar 215 to busbar 235, the width of the module W_m 563,the number of cells Nc_sub 564 in the suboptimal regions 211, 231, theseparation Wc_seg 565 between waveform segments, the surface S_sub 566of the suboptimal regions 211, 231, and the surface Sc_sub 567 of thesuboptimal hatched out region described in FIGS. 2I, 2J. Step 551represents that of a first minimization of the sub-optimal area insuboptimal regions 211, 231. The minimization process is ordinarilyiterative and starts with a preliminary design where cells in suboptimalregions 211, 231, of zones 210, 230, have a surface that is larger by aratio Rc_sub, preferably where Rc_sub=0.07 (7 percent), than cells ininternal zone 220. An example of the computation follows:

Wc=L _(—) m/(Nc _(—) m+Rc_sub×2×Nc_sub),

Wc_seg=Cw×(1+Rc_sub),

h=Nc_sub×Wc,

α=arcsin(Wc_seg/Wc),

λ/2=h×tan(α),

N _(—) hp=Round(W _(—) m/λ/2),

λ/2=h/N _(—) hp,

α=arctan(λ/2/h),

Wc_seg=Wc×sin(α),

where W_m is module width, N_hp is number of half periods.

A photovoltaic efficiency maximization computation for module 100 thentakes place at step 552 using results N_hp 571, α 572, λ 573, and Wc574. Said efficiency maximization uses a mesh, for example a triangularmesh as represented in FIG. 4C, and an iterative finite-elementoptimization method to maximize the photovoltaic efficiency η 578 ofmodule 100. A person skilled in the art knows than many designparameters can be adjusted using a variety of numerical optimizationmethods. FIG. 5B therefore lists only the most important set of valuesoutput by said second optimization 552, namely: result 575Wc_sub_div_(i=1 . . . Nc_sub) representing the distance between adjacentmonolithic interconnect lines 250 at the divergent side of a waveform'shalf-period for cells 1 to Nc_sub comprised within regions 211, 231, asillustrated in FIGS. 4B and 2J; result 576 Wc_sub_con_(i=1 . . . Nc_sub)representing the distance between adjacent monolithic interconnect lines250 at the convergent side of a waveform's half spatial period for cells1 to Nc_sub comprised within regions 211, 231, as illustrated in FIGS.4B and 2J; result 577 Wc which may be an adjusted value for result 574Wc resulting from step 551.

ADVANTAGES OF THE INVENTION

The exemplary embodiments represented in the present disclosure offer anumber of advantages for the manufacture of monolithicallyinterconnected modules and especially the manufacture of a class offlexible monolithically interconnected modules. Such monolithicallyinterconnected modules may comprise series-interconnected optoelectronicdevices that are connected together in series, parallel, or acombination of both.

A main first advantage of the invention results from the absence offront-contact grid lines or at least from a reduction in the area wherefront-contact grid lines are needed when compared to conventionalmonolithically interconnected modules composed of rectangularphotovoltaic cells or optoelectronic devices.

A second advantage is cost reduction. This cost reduction results fromthe reduction or canceling of the effort needed to design said grids.

A third advantage is the reduction or canceling of some manufacturingsteps. This manufacturing simplification results from the reduction orcanceling of the effort needed to deposit a grid onto the front-contact.

A fourth advantage is, for a class of photovoltaic modules, increasedmodule efficiency. This efficiency increase results from an increase inthe light-exposed area of the semiconducting photovoltaic layer.

A fifth advantage is an increase in manufacturing yield. This yieldincrease results from a reduction in the number of elements, namely areduction or suppression of grid elements, needed for a photovoltaicmodule.

A sixth advantage is an increase in overall reliability of flexiblethin-film photovoltaic devices. This increased reliability results froma reduction in the number of points of failure introduced by theaddition of front-contact grids on flexible photovoltaic devices.

A seventh advantage is that, compared to thin-film photovoltaic modulescomprising uniformly straight cells, the module's voltage may bedecreased thanks to a reduction in the number of serially-interconnectedcells.

An eighth advantage is that, compared to photovoltaic devices featuringvisible front-contact grid lines, devices manufactured according to theinvention may contain no or fewer front-contact grid lines and thereforepresent a more uniform appearance that may be more pleasingesthetically.

A ninth advantage is that, compared to photovoltaic devices based onstraight line monolithic interconnects or more generally torectangular-shaped photovoltaic devices, devices manufactured accordingto the invention may provide improved electrical properties forphotovoltaic devices featuring curved contours.

A tenth advantage is that, compared to rectangular photovoltaic devices,devices manufactured according to the invention enable increasedcoverage of non-rectangular surfaces featuring curved or obliquecontours, thereby maximizing the area producing photovoltaic electricityand increasing the fill factor of the overall photovoltaic installation.

1. A thin-film optoelectronic module device, comprising at least three optoelectronic components or cells, such as photovoltaic, diode, or light-emitting diode components, that are monolithically interconnected in series and such that when viewed along a viewing axis substantially orthogonal to the optoelectronic surface of said thin-film optoelectronic module device, at least one monolithic interconnect line, delimited by an isolating back-contact groove in the electrically conductive back-contact layer and an isolating front-contact groove in the electrically conductive front-contact layer, represents a curve depicting a spatial periodic or quasi-periodic wave of at least one spatial half-period, the largest peak-to-peak amplitude of which is at least eight times that of the shortest distance between said back-contact groove and said front-contact groove of said monolithic interconnect line and wherein, between a first busbar and a second busbar of the optoelectronic module device, the optoelectronic surface of said thin-film optoelectronic module device presents at least one set of at least three zones of substantially parallel monolithic interconnect lines that each depict a periodic or quasi-periodic wave of at least one spatial half-period having a largest amplitude wave component or a baseline largest amplitude wave component of spatial period λ, said set being visually segregated into: (a) an internal zone comprising at least one monolithic interconnect line which optionally delimits the internal zone and, (b) border zones, between the internal zone and each busbar, each border zone comprising at least one monolithic interconnect line that is substantially parallel to monolithic interconnect lines of said internal zone and where the amplitude of said largest amplitude wave component of at least one said monolithic interconnect line within said border zones is decreased with respect to that of the adjacent monolithic interconnect line that is closer to or comprised in said internal zone, and decreases for each said line that is located closer to the optoelectronic module device's busbar, wherein within the border zones there is a lower front-contact sheet resistivity than in the internal zone.
 2. A device, according to claim 1, which comprises an electrically insulating layer positioned either as a substrate under, or as a superstrate on top of, the following stack of layers (a), (b), (c): (a) a front-contact layer comprising at least one first and at least one second electrically conductive front-contact components, said first and second front-contact components being separated by at least one front-contact groove making at least one first front-contact component and at least one second front-contact component that are electrically separate; (b) an absorber layer comprising at least one semiconductive optoelectronically active layer; (c) a back-contact layer comprising at least one first electrically conductive back-contact component and at least one second electrically conductive back-contact component deposited onto said electrically insulating layer wherein said first back-contact component and second back-contact component are separated by at least one back-contact groove making said first back-contact component and second back-contact component electrically separate, thereby realizing a first optoelectronic component and a separate second optoelectronic component each comprising a stack of said front-contact component, at least one said semiconductive layer, and said back-contact component; and such that at least one monolithic interconnection connects at least one of said first front-contact components, passing through said semiconductive layer, with at least one of said second back-contact components, thereby realizing a series-interconnection between a first optoelectronic component and a second optoelectronic component.
 3. A device, according to claim 1, wherein at least one said back-contact groove or at least one said front-contact groove that, when viewed along a viewing axis substantially orthogonal to the optoelectronic surface of said thin-film optoelectronic module device represented by at least one monolithic interconnect line, depicts a curve comprising at least one peak of triangular shape.
 4. A device, according to claim 1, wherein at least one said back-contact groove or at least one said front-contact groove that, when viewed along a viewing axis substantially orthogonal to the optoelectronic surface of said thin-film optoelectronic module device, represented by at least one monolithic interconnect line, depicts a curve comprising at least one peak of rounded shape, said peak having a radius of curvature that is less than the peak's width at tenth of maximum amplitude.
 5. A device, according to claim 1, wherein at least one said monolithic interconnect line comprises at least one additional wave of spatial period smaller than half of that of said largest amplitude wave component.
 6. A device, according to claim 1, wherein at least one said monolithic interconnect line is drawn to substantially correspond to a mathematical mapping of at least one other said monolithic interconnect line.
 7. A device, according to claim 1, wherein at least one said monolithic interconnect line is drawn to substantially correspond to a mathematical radial transformation of at least one other said monolithic interconnect line.
 8. A device, according to claim 1, further comprising at least one metalized grid component made of at least one metalized trace deposited onto at least one said front-contact component.
 9. A device, according to claim 1, wherein a line segment comprised within said monolithic interconnect line is a continuous groove filled with conductive material and substantially parallel to a monolithic interconnect line.
 10. A device, according to claim 1, wherein at least one semiconductive photovoltaic layer 130, known as the absorber layer, is made of Cu(In,Ga)Se₂ semiconductor hereinafter referred to as CIGS.
 11. A device, according to claim 1, wherein a line segment comprised within said monolithic interconnect line is a segmented line of holes substantially representing a dash pattern that is substantially parallel to the monolithic interconnect line and wherein at least one of said holes comprises a wall made of a copper-rich amorphous metallic compound of solidified CIGS melt stemming from said semiconductive optoelectronically active layer made of CIGS material.
 12. A method for the design of thin-film optoelectronic module devices comprising at least three series-interconnected optoelectronic components or cells, such as photovoltaic, diode, or light-emitting diode components, the method comprising monolithically interconnecting said components in series such that when viewed along a viewing axis substantially orthogonal to the optoelectronic surface of said thin-film optoelectronic module device, at least one monolithic interconnect line, delimited by an isolating back-contact groove in the electrically conductive back-contact layer and an isolating front-contact groove in the electrically conductive front-contact layer, represents a curve depicting a spatial periodic or quasi-periodic wave of at least one spatial half-period, the largest peak-to-peak amplitude of which is at least eight times that of the shortest distance between said back-contact groove and said front-contact groove of said monolithic interconnect line and wherein, between a first busbar and a second busbar of the optoelectronic module device, the optoelectronic surface of said thin-film optoelectronic module device presents at least one set of at least three zones of substantially parallel monolithic interconnect lines that depict a periodic or quasi-periodic wave of at least one spatial half-period having a largest amplitude wave component or a baseline largest amplitude wave component of spatial period λ, said set being visually segregated into: (a) an internal zone comprising or delimited by at least one monolithic interconnect line and, (b) border zones, between the internal zone and each busbar, said border zones each comprising at least one monolithic interconnect line that is substantially parallel to monolithic interconnect lines of said internal zone and where the amplitude of said largest amplitude wave component of at least one said monolithic interconnect line within said border zones is decreased with respect to that of the adjacent monolithic interconnect line that is closer to or comprised in said internal zone, and decreases for each said line that is located closer to the optoelectronic module device's busbar, providing border zones wherein there is a lower front-contact sheet resistivity than in the internal zone: said method further comprising the iterative computation of the number of said cells of said thin-film optoelectronic module device, the width of said cells, and, within at least one border zone over a peak-to-peak half spatial period λ/2 of said quasi-periodic wave of at least one pair of substantially parallel monolithic interconnect lines, the distance between cells at the divergent and convergent sides of at least one of said wave's peak-to-peak half spatial period.
 13. A method according to claim 12, comprising for said optoelectronic module device positioning an electrically insulating layer either as a substrate under, or as a superstrate on top of, the following stack of layers (a), (b), (c): (a) a front-contact layer comprising at least one first and at least one second electrically conductive front-contact component, said first and second front-contact components being separated by at least one front-contact groove making at least one first front-contact component and at least one second front-contact component that are electrically separate; (b) an absorber layer comprising at least one semiconductive optoelectronically active layer; (c) a back-contact layer comprising at least one first electrically conductive back-contact component and at least one second electrically conductive back-contact component deposited onto said electrically insulating layer wherein said first back-contact component and second back-contact component are separated by at least one back-contact groove making said first back-contact component and second back-contact component electrically separate, thereby realizing a first optoelectronic component and a separate second optoelectronic component each comprising a stack of said front-contact component, at least one said semiconductive layer, and said back-contact component; and such that at least one monolithic interconnection connects at least one of said first front-contact components, passing through said semiconductive layer, with at least one said second back-contact components, thereby realizing a series-interconnection between a first optoelectronic component and a second optoelectronic component.
 14. A method according to claim 12, wherein computation of at least one dimension that represents a characteristic size of the optoelectronic cells is carried out using input values for front-contact sheet resistivity, back-contact sheet resistivity, initial cell width, and monolithic interconnect line width.
 15. A method according to claim 12, wherein computation of at least one dimension that represents a characteristic size of the optoelectronic cells is carried out using at least one repeatable computation of the photovoltaic characteristics of a cell segment model, said cell segment model comprising at least one finite element cell segment.
 16. A method according to claim 12, wherein computation of at least one dimension that represents a characteristic size of the optoelectronic cells comprises at least one repeatable computation where photovoltaic conversion efficiency of the thin-film optoelectronic module device is maximized. 